Research On Shielding Performance Analysis And Design Methods Of Electronic Equipment

With the rapid developments of high-speed electronic technology and the widespread applications of wireless technology in recent years, electromagnetic interference(EMI) problems are becoming increasingly prominent. Consequently, electromagnetic compatibility(EMC) of electronic systems turns out to be of great importance in modern design process. Electromagnetic shielding is of top priority in EMI control and is a preferred design method in EMC. This dissertation studied on the shielding mechanisms of frequently used structures, developed several fast computational schemes for predicting the shielding performance of equipment enclosures, and proposed some strategies for enhancing the shielding capability of electronic equipment based on extensive analysis. The topics covered in this dissertation include:(1)Study on the analytical methods for predicting the shielding effectiveness of enclosures with slot or aperture array.The traditional equivalent circuit models treat the aperture as a coplanar strip transmission line, get its impedance by quasi-static approximation, and then obtain the shielding effectiveness at monitor point by transmission line theory. However, this method was proved inaccurate or even failed in some special cases. Therefore, the existing analytical formulations for predicting the shielding effectiveness of enclosures with slot or aperture array were reviewed extensively to provide their advantages, drawbacks, and application scope. After that, a more accurate and robust model based on transmission line theory and waveguide diaphragm theory was proposed. This new model was further generalized to account for higher order modes, and thus can handle enclosures operating at higher frequencies.( 2) Study on the numerical analysis and design methods for shielding performance of enclosures with slot or aperture array.The existing researches on the shielding performance of enclosures mostly focus on numerical methods themselves. Few literatures about the influences of geometric parameters of slot or aperture array, properties of interference wave, and inner loading effect on the shielding performance of enclosures can be found. In view of this situation, the radiating and scattering properties of slot and aperture array were studied. Along with that, the resonance properties of enclosures with slot or aperture array were investigated. Moreover, the shielding performances of enclosures with slot under interior excitation and enclosures with aperture array under exterior plane-wave excitation were studied extensively using the transmission-line matrix modeling(TLM) method. Some important factors such as the slot dimensions, aperture array dimensions, properties of interference wave, and inner loading effect were investigated to find their influences on the shielding performance of enclosures. After that, some general strategies for enhancing the shielding capability of enclosures were proposed. Finally, two server boxes were modeled and tested to validate the numerical models.(3)Study on the finite-element time-domain modeling and analysis methods for shielding structures under interior excitation.Among various numerical methods that are applicable to simulate electromagnetic shielding problems, the finite-element time-domain(FETD) method possesses unmatched advantage in handling arbitrary geometry, material complexity, and broadband excitation. Therefore, Galerkin’s method was adopted to derive the functional of shielding systems under interior coaxial cable excitation. The functional was further discretized in the time domain to obtain an unconditionally stable time-marching scheme. Moreover, an object-oriented program was developed to compute the delivered power and the electric far field of enclosures with slot or aperture array. The measurement results were also presented to verify the computation results and validate the numerical models.(4)Study on the combination of FETD and extended Prony’s method for the shielding analysis of highly resonant shielding structuresIn applying the time-domain methods to study electromagnetic response of shielding systems, the accuracy of the frequency-domain quantities is compromised if the transient time record is terminated too prematurely. On the other hand, the transient time record may be required over tens of thousands or even hundreds of thousands of time steps if pure time-domain numerical method is adopted. Therefore, the resonance mechanisms of highly resonant enclosures were first studied intensively. After that, the combination of FETD and the extended Prony’s method was proposed to reduce the number of iterations and computational time efficiently. Moreover, the delivered power and the electric far field of enclosures with slot or aperture array were computed using the combined method. As shown by the comparison with the pure FETD method, the combined method achieved the same order of accuracy with a time record computed over a much shorter time. Furthermore, the procedure and details of using this combined method to investigate the shielding properties of highly resonant enclosures were demonstrated extensively. Finally, some rules about selecting crucial parameters were proposed.(5)Study on the parallel algorithms of FETD for shielding analysis based on GPUFew literatures about the numerical modeling of shielding problems by FETD can be found. There are two potential reasons responsible for this phenomenon. The first one refers to massive computational burden of FETD. The second is present because it takes much effort to develop a robust FETD code. In view of these difficulties, it is necessary to accelerate the FETD solving process by parallel computation. Assembling and solving processes are the most time consuming stages in the entire FETD computation. Therefore, this dissertation developed efficient parallel algorithms to accelerate these two stages. The accelerated FETD was then employed to compute the delivered power and the electric far field of enclosures with slot or aperture array. Moreover, the speedup of the accelerated FETD against the traditional FETD was studied extensively. Finally, some strategies for enhancing the parallel efficiency were proposed.The originalities of this dissertation can be summarized as follows:(1)The analytical formulations with better accuracy and flexibility for the prediction of shielding effectiveness of enclosures with aperture or slot were proposed.The waveguide diaphragm model proposed in this dissertation is more accurate and robust than the traditional models. It eliminates the constraints on the geometry of slot and aperture, and can handle the special case that the length of slot equals to an integer multiple of wavelength. Moreover, the new model is more accurate than traditional models since it accounts for the propagation of the higher order modes.(2)The shielding design methods were proposed for enclosures with slot or aperture array.The shielding performances of enclosures with slot under interior excitation and enclosures with aperture array under exterior plane-wave excitation were studied comprehensively in this dissertation. Moreover, the important factors such as the slot dimensions, aperture array dimensions, properties of interference wave, and inner loading effect were investigated to find their influences on the shielding performance of enclosures. Finally, some general strategies to enhance the shielding capability of enclosures with slot or aperture array were proposed.(3)A combination of FETD and extended Prony’s method for the shielding analysis of highly resonant shielding structures was proposed.The combined method proposed in this dissertation can achieve the same order of accuracy with the direct FETD computation while consuming much shorter time. Moreover, the procedure and details of using this combined method and some rules about selecting the parameters were proposed.(4)Some parallel algorithms of FETD based on many core GPU were proposed.This dissertation proposed some parallel algorithms of FETD on GPU and investigated its speedup against the traditional CPU program. For the aperture array shielding problem with about 1.7 million unknowns, 22 times speedup against CPU program was achieved on single GPU.